This project will develop methods that can be used with computerized hospital data-reporting systems to improve our understanding of the costs of care and patterns of resource utilization for AIDS patients. All AIDS cases in a database containing discharge abstracts and itemized bills for all discharges from Philadelphia's five medical school teaching hospitals over a two-and-one-half year period will be identified for this project. Identification methods will include a review of diagnoses and demographic information on each admission, in conjunction with review of the Philadelphia Department of Public Health's list of known cases, and each hospital's list of known cases. Existing methods for assigning AIDS patients to subgroups that are clinically meaningful and predictive of hospital-resource utilization -- such as disease staging for AIDS -- will be evaluated. Costs of care will be measured using ratio of costs- to-charges times charges methods, and compared with costs as determined by a microcosting system available at one of the participating hospitals. AIDS resource consumption also will be studied by counting the number of each specific hospital service (e.g. intensive care days, x-rays, CBCs, pharmaceutical products, etc), and examining the relationships between costs and intensity of utilization of these specific services. Finally, resource consumption patterns within hospitals over time, and between hospitals, will be compared, both for the total AIDS population, and for clinically meaningful subgroups. Although the project will yield increased understanding of the costs of AIDS care and changing patterns of resource consumption in a subset of Philadelphia's hospitals, the primary goal of the project is to develop and evaluated methods for use in follow-up studies. Therefore, we will assess whether the differences found warrant expansion of the pilot project to larger studies of regional, statewide, and national databases.